Field of the Invention
The invention relates to a motor control device and a motor control method using a position detection signal, and more particularly, to control of the drive start of a motor.
Description of the Related Art
Stepping motors having characteristics of, for example, small size, high torque, long life are widely used in cameras, optical disk devices, printers, or projectors because they can easily perform digital positioning operation by open-loop control. As a solution to a large load on a motor or step-out upon a high-speed rotation, there is a method in which an encoder is attached to the stepping motor, energization is switched in accordance with the position of the rotor, and thereby, the operation of what is referred to as a “brushless DC motor” is performed.
Japanese Patent Application Laid-Open Publication No. 2002-119089 discloses a method for applying a rectangular wave-shaped drive waveform to the stepping motor, and Japanese Patent Application Laid-Open Publication 2014-045646 discloses a method for applying a sine wave-shaped drive waveform to the stepping motor. A high speed and high torque can be achieved while preventing step-out by effectively applying the drive waveform to a magnetization phase of the rotor, by using an encoder signal that is output in response to the rotation of the rotor.
In the prior art, before the encoder signal is detected, it is impossible to perform the operation equivalent to what is referred to as a “brushless DC motor” (hereinafter, referred to as “advance angle control”). Accordingly, between the drive start and the detection of the encoder signal, open drive of the stepping motor is performed. During the period of this open drive, the torque for acceleration is not applied, and if the length of the period affects the acceleration time, it takes a long time to start the operation.